Substrate metallization and ball attach metallurgy with a novel dopant element

Abstract

Surface-active dopants are added to a portion of a circuit package before a reflow process to promote wetting and reduce the formation of solder bump bridges. The circuit package has a solder element that electrically connects the circuit package to a substrate. A reflow process is performed to attach the solder element to a pad on the circuit package. During the reflow process, the surface-active dopants diffuse to the surface of the solder element and form an oxide passivation layer on the surface of the solder element.

What is claimed is: 
     
       1. A method comprising:
 forming a layer of surface-active dopants between two metal layers of a pad that is to be bonded to a solder element in a circuit package; 
 performing a reflow process by heating the circuit package above a melting temperature of the solder element; and 
 activating the surface-active dopants by the heating to cause the surface-active dopants to diffuse to a surface of the solder element and to form an oxide passivation layer on the surface of the solder element. 
 
     
     
       2. The method of  claim 1 , wherein the surface-active dopants are selected from Germanium (Ge), Boron (B) and Rhenium (Re). 
     
     
       3. The method of  claim 1 , further comprising: depositing the surface-active dopants into the solder element before the reflow process. 
     
     
       4. The method of  claim 1 , further comprising: depositing the surface-active dopants into solder paste between the solder element and the pad before the reflow process. 
     
     
       5. The method of  claim 1 , further comprising:
 performing a subsequent reflow process to bond the circuit package to a substrate; and 
 removing the oxide passivation layer by flux during the subsequent reflow process. 
 
     
     
       6. The method of  claim 5 , wherein the subsequent reflow process is a surface mount (SMT) reflow process. 
     
     
       7. The method of  claim 1 , wherein the reflow process is a ball attach reflow process for attaching the solder element to the pad.